1. Field of the Invention
This invention relates to gas discharge type underwater hammers and more particularly it concerns novel underwater hammer constructions having improved driving characteristics.
2. Description of the Prior Art
Prior art gas discharge type underwater hammers are shown and described in U.S. Pat. No. 3,958,647 to Stephen V. Chelminski. Other patents in this field are U.S. Pat. Nos. 3,604,519; 3,646,598; 3,714,789; 3,721,095; 3,788,402; 3,817,335 and 3,892,279. In general, a gas discharge type underwater hammer comprises an elongated guide tube, a massive ram that is driven up and down in the tube, an anvil in the tube which is hammered upon by the ram and a gas discharge device positioned between the ram and the anvil. When the gas discharge device is triggered, it releases a charge of highly compressed gas which drives the ram upwardly in the guide tube. When the pressure of the gas dissipates and the ram loses its upward momentum it falls back onto the anvil; and the striking force of the ram on the anvil drives the pile, or other element on which the anvil is mounted, downwardly. The gas which is used to drive the ram upwardly in the guide tube is exhausted from the hammer during each cycle through an annular clearance between the ram and the guide tube; and the region under the ram is reflooded prior to the next gas discharge by a flow of water shown through a central passageway in the ram.